In the field of an all-solid-battery, conventionally, a sulfide-based solid electrolyte material has been known. For example, Patent Document 1 reports that, by mixing Li2S and P2S5 at a specific molar ratio (68:32 to 73:27), subjecting the mixture to a mechanical milling treatment, followed by a heat treatment, glass ceramics electrolyte particles having a high ionic conductivity (2×10−3 S/cm or less) can be obtained. However, this material tends to be easily hydrolyzed (it generated hydrogen sulfide by contacting water), and hence, the use thereof in a high dew point environment is limited.
A technology of suppressing this tendency of being hydrolyzed is proposed in Patent Document 2. However, this technology has a problem that the ionic conductivity is greatly lowered when suppressing hydrolyzability.